Frequencies used for information equipment including network units and a personal computers have been remarkably improved recently and are newly reaching a gigahertz band from a megahertz band. Thereby, a signal analysis considering influences of various noises is also requested for a high-frequency signal for transmitting the wiring pattern of a printed circuit board.
A circuit designer of an integrated circuit or the like selects a circuit device constituting a circuit or the value of a parameter for controlling the characteristic of the circuit device.
At present, a circuit simulator is used when designing circuits. The circuit simulator simulates a circuit operation on a computer without fabricating an actual circuit and shows the circuit operation for a designer. The simulator operated by the software referred to as SPICE2 developed by University of California at Berkley in 1972 is publicly known.
For example, the circuit simulator executes simulation in accordance with the connection data between circuit devices constituting a circuit to be analyzed and device parameters to estimate an amount of noise under a predetermined operational state of each circuit device and display or print the estimated number of noises.
As described above, the conventional circuit simulator is good for the waveform analysis up to approx. 100 MHz and is greatly supported by various designers. Because frequencies of information equipment have been remarkably raised recently and are reaching a gigahertz band from a megahertz band, a waveform analysis considering influences of various noises is requested for a high-frequency signal for transmitting a wiring pattern to a printed circuit board.
The skin effect is a typical one influencing a transmission waveform in a high-frequency band (approx. 300 MHz or higher). This is a phenomenon in which current is concentrated on the surface of a printed circuit board and resultantly a resistance component increases to cause a waveform distortion. That is, in the graph G shown in FIG. 15, the waveform L1 denotes a result of performing an analysis by a circuit simulator without considering the skin effect. The waveform L2 denotes a result of performing an analysis by a circuit simulator by considering the skin effect. As shown in the graph G, a large difference is produced in the rise of a waveform which is an analysis result between a case of considering the skin effect and a case of not considering the skin effect.
In the case of a conventional circuit simulator, however, an analysis is performed by using a loss transmission-line element referred to as a high-frequency element in order to perform the analysis by considering the skin effect. In this case, when modeling an actual wiring pattern, a portion (curved portion) in which specifications of a wiring pattern are changed is modeled into a micro high-frequency element having an unexpectedly small wiring length. In this case, it is a problem that waveform analysis time increases as the number of micro high-frequency elements increases.
Therefore, when considering the skin effect, that is, when performing an analysis correspondingly to a high frequency, a convention circuit simulator is not practical because a wave analysis requires approx. 3,000 hr due to influences of the micro high-frequency element.